[Feature] Close table metrics when table is dropped

### Search before asking

- [X] I searched in the [issues](https://github.com/apache/incubator-paimon/issues) and found nothing similar.

### Motivation

Unregister the table metrics when table is dropped, otherwise the reported metrics can be polled by client still, like Prometheus.

### Solution

_No response_

### Anything else?

_No response_

### Are you willing to submit a PR?

- [X] I'm willing to submit a PR!

No files, tests, or entry points are identified in the issue. Trace where table-drop handling and table-metric registration are implemented, then verify that dropping a table prevents clients such as Prometheus from polling its metrics.

Written by the indexing model from the issue text.